1. Field of the Invention
The present invention relates to a container such as a bottle, pouch, or tube for products of a liquid-to-pasty consistency. Such containers are used in particular for the packaging of cosmetic products, such as shampoos, care creams, lotions, or pastes such as tooth pastes.
2. Discussion of the Background
In packaging and bottling fields, and particularly in cosmetics, one is always working to find novel and original packaging means. Additional steps of decorating containers and bottles is often relied upon. However, these steps increase costs of manufacture and, in a case of containers made of a plastic material, do not always give a very satisfactory aesthetic result.
Bottles and containers have been proposed having at least one relatively narrow strip orientated along a main axis of the bottle and made of a material of a color different from a color of material forming a remainder of the container. Apart from its aesthetic nature, by using a translucent material this longitudinal strip may make it possible to let a user know how much product remains in the container. Moreover, a zone of a different color may be used to indicate to the user the place where it is desirable to squeeze the bottle so as to optimize emptying the container. Such a container with a translucent strip is described, for example, in EP-A-0 508 168 or in U.S. Pat. No. 343,568.
Again, by way of example, EP-A-0 385 942 describes a bottle obtained by extrusion blow molding from a parison of which at least one strip is made of a material of a hardness different from a hardness of the rest of the material, so as to impart better rigidity to the final structure of the bottle.
Typically, such containers are generally made by blow molding a tubular blank obtained by extrusion or injection molding. In the case of a container made of two materials the blank or parison may be obtained by coextrusion or duplex injection molding.
In extrusion technology, plastic materials are heated and subjected to pressure by a screw/sleeve assembly so as to provide, by means of an extrusion head, a tubular blank in a form of a hot parison. This tubular blank is subsequently placed between two female half molds which have the required shape to mold the desired container, and blow molding permits shaping of the parison as it expands under pressure and assumes the shape defined by the mold. cooling permits the material to set in the shape thus obtained.
In the case of coextrusion, the extrusion head is fed by two feeding channels so that the parison has a narrow strip of a material of a different composition and/or color, the initial width of the strip in the parison being calculated according to a desired width of a strip on the container. In fact, as increased material is forced by blow molding to move away from its initial position, an increased amount of material is stretched and refined in width and thickness.
With the injection molding technology, or more precisely duplex injection technology, in the case of a container made of two materials including a longitudinal strip, a tubular blank generally called a "preform" is created in a mold wherein a part of a bottle formed by the first material is molded in the first step. Means in the form of a mold slide prevent this first material from flowing into a zone corresponding to the longitudinal strip. The mold slide is then withdrawn and the second material is cast into a thus vacated volume so as to form the longitudinal strip.
One of the problems linked to these technologies is illustrated in FIGS. 1A-1C. The container shown is a bottle of a type comprising a body 1 with a longitudinal axis X, closed at one of its ends by a bottom 2 and surmounted by a neck 4 to which the body is joined by a shoulder 3. The neck 4 has a thread 5 intended to receive in a detachable manner a stopper (not shown).
A cross-section of the bottle illustrated in FIG. 1B has an elongate shape and has a major axis A and a minor axis C. One of the edges 11 parallel to the minor axis C is constituted by a strip of material of a color different from a color of the rest of the bottle. As shown in FIG. 1A, the resulting differently colored strip is not straight, but has borders with the rest of the bottle which fluctuate around a median position.
FIG. 1C shows an enlargement area 10 of the edge of the cross-section of the bottle (delimited by the enlargement area 10 of FIG. 1B). Thus, although it is desirable to have a differently colored strip delimited by straight edges, in practice, each one of the lateral edges 40, 41 of the strip fluctuates between a minimum position B" and a maximum position B'. The variations produce a visual effect that does not give a clear-cut impression, and may adversely affect perception of potential clients regarding contents of the container.
The above fluctuations are linked to the manufacturing process and may be explained in particular by micro air currents and temperature gradients which may have a significant influence on movements of the parison. Similarly, small variations in density inside the materials themselves, or small temperature variations, may affect the fluidity and expansion potential of the materials, producing variations in width of the strip of different color and/or kind.
The above variations are more noticeable, when the strip 12 differs in color from the rest of the bottle. They may also be more noticeable and an additional drawback when the materials are of a different appearance. For example, if the longitudinal strip is made of an elastomer of a matte appearance to improve gripping of the bottle, while the rest of the bottle has a rather shiny appearance, the fluctuations of the edges of the strip will be more visible. similarly, the longitudinal strip may have a granular appearance, while the rest of the container has a smooth appearance, or vice versa.
Another problem occurring in the field of packaging and bottling, in particular in the field of cosmetics, relates to holding the package or bottle in the hand, in particular in conditions where, for example in the case of a shampoo, the user has wet hands. For this purpose, a special shape is utilized that follows a shape of the hand. There also exist bottles which have an extra layer of an elastomeric material at certain points, for example. However, these systems have a drawback of complicating the manufacturing process, substantially increasing the manufacturing cost of these containers. If the improved gripping zone is obtained during molding by coextrusion/blow molding, in a form of one or several longitudinal strips, there then arises the problem of distinctness of the lateral edges of the strips such as described above.